I. Field of the Invention
A turbofan jet engine functionally comprises an air inlet duct, a fan, a compressor, a combustion chamber, a turbine and an exhaust nozzle. These various elements are contained in the casings.
The turbofan jet or turbojet engine also comprises an internal secondary flow casing around these casings, in the form of a ring that contains the secondary airflow on its external surface. The secondary airflow corresponds to air entrained by the fan that does not penetrate into the compressor. This ring comprises means of opening into two half-shells, so that the core of the turbojet engine can be accessed. The core of the turbojet engine means elements in the turbojet engine located within the chamber defined by the internal secondary flow casing.
Some fluids necessary for operation of the turbojet engine such as fuel and oil must be routed from the outside of the turbojet engine towards its core. These fluids are used particularly to supply the combustion chamber with fuel, the various elements of the engine with lubrication oil, various discharge valve actuation jacks, the compressor variable pitch, control of the clearance of high pressure and low pressure turbine casings, etc.
Fluids are routed through pipes commonly called ancillaries. The invention relates particularly to the passage of ancillaries along the support arm of a turbojet engine casing, called the intermediate casing.
II. Description of Related Art
FIG. 1 shows a partial view of a turbojet engine 1 according to prior art. This turbojet engine comprises the outer ring 2 of a so-called intermediate casing on the output side of the fan blade retention casing, to which the forward suspension of the turbojet engine is traditionally fixed to an aircraft. The intermediate casing also comprises radial arms 3. An inner ring 4 is arranged adjacent to its outer ring 2, this inner ring 4 comprising a bearing step 5 of the secondary flow inner casing, not shown.
Some ancillaries 6 have to be transferred from the outside of the intermediate casing to the core of the turbojet engine 1. This transfer is usually made along an arm 3 of the intermediate casing, the ancillaries 6 opening up in the core of the turbojet engine 1 at the inner ring 4.
The turbojet engine 1 presented will be installed on an aircraft with a fairly small ground clearance. Therefore, its nacelle is flattened near the bottom and spreads out on its sides. For safety reasons, the ancillaries 6 must not pass in the bottom part of the turbojet engine 1, if the turbojet engine 1 rubs along the ground. Therefore, they are routed along an arm 3 of the intermediate casing separated from the global vertical plane of symmetry of the turbojet engine 1.
The ancillaries 6 pass through the outer ring 2 of the intermediate casing and are contained between the outer ring 2 and the inner ring 4 within an arm 7, which protects them and guides the secondary airflow. The ancillaries 6 are fixed at the inner ring 4 onto a plate 8, by nuts on each side of the plate 8.
There is a fairly large number of these ancillaries 6, for example there may be eleven, and they must be guided in a fairly congested area. Furthermore, they cannot be located outside the section defined by projection on the transverse plane of the support arm 3 of the intermediate casing, in a plane transverse to the turbojet engine axis, for aerodynamic reasons related to the secondary airflow. Therefore, they have to be spread longitudinally on the plate 8. The plate 8 extends longitudinally beyond the inner ring 4 and projects into the opening area of the secondary flow internal casing cowls, particularly due to the surface area necessary for screwing the nuts, since it cannot be located in the vertical plane of symmetry containing the cowl opening hinge, as we have seen above.
Therefore, a recess has to be formed on a cowl of the inner secondary flow casing, for the plate 8 to pass through when the cowls are opened and closed. The part 8 must be adapted and must fill this recess, to assure continuity of the airflow guidance between the inner ring 4 and the surface of the inner secondary flow casing, at the recess. Production costs of the said casing and maintenance cost of the turbojet engine are correspondingly increased.